1st January 2009, 02:21 PM
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|  Kew Gardens Oaks under threat
Seems climate change, pests and fungi are taking their toll. Oak tree deaths herald new pest threat to traditional plants, Kew curator warns - Telegraph Quote: |
Oak tree deaths herald new pest threat to traditional plants, Kew curator warns
Traditional British plants from the oak tree to the garden cabbage are under threat because of the effects of climate change, the curator of Kew Gardens has warned.
Dozens of oaks, many of them as old as 150 years, have had to be cut down at Kew in the last few years because of a beetle infestation which leaves the inside of the trunk looking "like honeycomb".
Outdoor vegetable patches have been under attack all year round from pests previously only found in greenhouses.
Meanwhile new invaders, such as a fingernail-sized insect which attacks wisteria, have been spreading as a result of milder winters and a looser controls on plants coming into the country from abroad, he added.
Dr Nigel Taylor, curator of the Royal Botanic Gardens at Kew, said that despite cold weather in recent days, a succession of mild winters had helped both native and exotic pests to gain a foothold.
"The impression is becoming more and more confused," he said.
"The seasonality is disappearing so that apart from day length, which is a clue to what time of year you are in, sometimes it is hard to guess when you look at the weather."
The full effect of a series of heatwaves earlier this decade, including the record summers of 2003 and 2006, are only now being felt with an spate of giant oak trees dying.
Kew has lost about 40 trees in the last three years because of infestation by thousands of oak pinhole borers, a beetle larvae which have been spreading undetected since the droughts originally weakened the plants' natural defences.
One 150-year-old Hungarian oak, which was one of the oldest and biggest trees at Kew, had to be cut down a few weeks ago after suddenly succumbing to the pest. When it was cut open it was "riddled" with the larvae.
"We are removing more than a dozen mature oaks a year at present and have been for the past three years," he said.
"I think mature oaks have been dying in increasing numbers around the country over the last few years as a consequence of the droughts."
Meanwhile chestnut trees have been under attack from both bleeding canker – a disease which has thrived amid milder winters – and a foreign moth called the horse chestnut leaf miner which made conkers fall earlier this year.
"Even in my vegetable plot at Kew I have had whitefly on my brassicas for the last 36 months," he added.
"This is a pest which you would normally associate with the greenhouse, not outdoors."
Experts are also worried about a possible invasion of the Asian Longhorned Beetle which has had a devastating effect on trees on North America.
Although it has not yet become established in the British Isles there have already been isolated cases.
At Kew a pest called the Giant Wisteria Scale, has spread from a house nearby to the gardens themselves.
"I think this is a product of the changing climate and the globalisation of plant movement, there was a time when Britain was effectively border controlled for plant health, that is not happening now," he said.
Staff at Kew are planning to impose a blanket quarantine on all new plants to stem the tide of alien invaders.
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